SIMMERING tension between the AFL and North Melbourne has erupted with Andrew Demetriou accusing the club of using intimidation to hasten a potentially damning - and costly - investigation of player Lachie Hansen's health and concussion management.

North and league bosses had remained tight-lipped on the sensitive proceedings until yesterday when Demetriou, fed up with the club's attitude, issued a warning to Drew Petrie for his outspokenness on the issue, and tabled his disapproval of coach Brad Scott's behaviour in a separate matter.

Singling out Petrie, who on Thursday suggested the AFL was making North's medical team look bad by taking more than a month to examine whether Hansen was managed appropriately following a round 20 head clash, Demetriou pointed out how the senior player had been a key trigger of the investigation.

''I just caution Drew,'' the AFL CEO said yesterday. ''This is an ongoing, serious investigation. Part of it that was a contributing factor was Drew Petrie saying Lachie Hansen was concussed, so Drew can't have it both ways.''

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Petrie was interviewed by one of the AFL's integrity officers after disclosing in a radio interview that he saw Hansen - who appeared to be unconscious when he crashed face-first into the Etihad Stadium turf following a collision with Essendon's Nathan Lovett-Murray - vomiting in the change rooms at half-time of the game. Hansen was subsequently sent back onto the field and kicked two final-term goals with North insisting he was not concussed. The club could be fined up to $20,000 if the investigation found Hansen should not have been redeployed.

The spotlight has stayed on the key forward given he was substituted out of North's round 23 game against Greater Western Sydney last weekend due to a first-term head clash that left him with blurred vision. North has said Hansen was not concussed in that incident either and he is set to play in tomorrow's final against West Coast.

The Saturday Age has been told the most recent delay in the investigation of the round 20 matter was caused after North cancelled a scheduled meeting between its doctor, Andy McMahon, and an independent concussion expert. Part of the club's frustration, according to one North boss, is the sense that the league has already conducted a broad inquisition - apparently interviewing more than 20 people - but is now requesting re-examinations with an expert who could have been employed from the beginning.

''North Melbourne, or any club … butt out of investigations,'' Demetriou said. ''I think there have been some comments which haven't been helpful. Ill-informed comments … designed to intimidate. These guys will go about their business thoroughly and do it professionally, and when they're finished they'll hand it down.''

Demetriou could not be reached for further comment, but in the radio interview on SEN he was also scathing of Scott's on-field abuse of GWS veteran James McDonald, which incurred the coach a $5000 suspended fine.